Re: [PATCH] Support backtrace () on IA-64, make it work even with -fomit-frame-pointer on AMD64

[Jakub Jelinek <jakub at redhat dot com>]

On Sat, Oct 04, 2003 at 02:15:46PM -0700, Ulrich Drepper wrote:
> Jakub Jelinek wrote:
> 
> 
> > 2003-10-03  Jakub Jelinek  <jakub@redhat.com>
> > 
> > 	* sysdeps/ia64/backtrace.c: New file.
> > 	* sysdeps/x86_64/backtrace.c: New file.
> 
> Doesn't work for me on ia64 with gcc 3.2.  At link time libgcc_eh.a and
> the unwind functions in libc collide.
> 
> To make things compile in the first place I had to extend unwind.h with
> at least the type definition of _Unwind_Trace_Fn.

Sorry, I only compiled it outside of glibc and there it worked.
Here is a better patch (built on amd64, passed make check, checked output
of a few sample proglets):

2003-10-05  Jakub Jelinek  <jakub@redhat.com>

	* sysdeps/ia64/backtrace.c: New file.
	* sysdeps/x86_64/backtrace.c: New file.
	* sysdeps/generic/unwind.h (_Unwind_Trace_Fn): New type.
	(_Unwind_Backtrace): New prototype.

--- libc/sysdeps/ia64/backtrace.c.jj	2003-10-03 14:36:36.000000000 +0200
+++ libc/sysdeps/ia64/backtrace.c	2003-10-05 11:41:34.000000000 +0200
@@ -0,0 +1,85 @@
+/* Return backtrace of current program state.
+   Copyright (C) 2003 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Jakub Jelinek <jakub@redhat.com>, 2003.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include <bits/libc-lock.h>
+#include <dlfcn.h>
+#include <execinfo.h>
+#include <stdlib.h>
+#include <unwind.h>
+
+struct trace_arg
+{
+  void **array;
+  int cnt, size;
+};
+
+static _Unwind_Reason_Code (*unwind_backtrace) (_Unwind_Trace_Fn, void *);
+static _Unwind_Ptr (*unwind_getip) (struct _Unwind_Context *);
+
+static void
+init (void)
+{
+  void *handle = __libc_dlopen ("libgcc_s.so.1");
+
+  if (handle == NULL)
+    return;
+
+  unwind_backtrace = __libc_dlsym (handle, "_Unwind_Backtrace");
+  unwind_getip = __libc_dlsym (handle, "_Unwind_GetIP");
+  if (unwind_getip == NULL)
+    unwind_backtrace = NULL;
+}
+
+static _Unwind_Reason_Code
+backtrace_helper (struct _Unwind_Context *ctx, void *a)
+{
+  struct trace_arg *arg = a;
+
+  /* We are first called with address in the __backtrace function.
+     Skip it.  */
+  if (arg->cnt != -1)
+    arg->array[arg->cnt] = (void *) unwind_getip (ctx);
+  if (++arg->cnt == arg->size)
+    return _URC_END_OF_STACK;
+  return _URC_NO_REASON;
+}
+
+int
+__backtrace (array, size)
+     void **array;
+     int size;
+{
+  struct trace_arg arg = { .array = array, .size = size, .cnt = -1 };
+  __libc_once_define (static, once);
+
+  __libc_once (once, init);
+  if (unwind_backtrace == NULL)
+    return 0;
+
+  if (size >= 1)
+    unwind_backtrace (backtrace_helper, &arg);
+
+  /* _Unwind_Backtrace on IA-64 seems to put NULL address above
+     _start.  Fix it up here.  */
+  if (arg.cnt > 1 && arg.array[arg.cnt - 1] == NULL)
+    --arg.cnt;
+  return arg.cnt != -1 ? arg.cnt : 0;
+}
+weak_alias (__backtrace, backtrace)
--- libc/sysdeps/x86_64/backtrace.c.jj	2003-10-03 15:02:54.000000000 +0200
+++ libc/sysdeps/x86_64/backtrace.c	2003-10-03 15:02:49.000000000 +0200
@@ -0,0 +1 @@
+#include "../ia64/backtrace.c"
--- libc/sysdeps/generic/unwind.h.jj	Thu Sep  4 03:45:02 2003
+++ libc/sysdeps/generic/unwind.h	Sat Oct  4 08:59:35 2003
@@ -130,6 +130,14 @@ extern void _Unwind_DeleteException (str
    e.g. executing cleanup code, and not to implement rethrowing.  */
 extern void _Unwind_Resume (struct _Unwind_Exception *);
 
+/* @@@ Use unwind data to perform a stack backtrace.  The trace callback
+   is called for every stack frame in the call chain, but no cleanup
+   actions are performed.  */
+typedef _Unwind_Reason_Code (*_Unwind_Trace_Fn)
+     (struct _Unwind_Context *, void *);
+
+extern _Unwind_Reason_Code _Unwind_Backtrace (_Unwind_Trace_Fn, void *);
+
 /* These functions are used for communicating information about the unwind
    context (i.e. the unwind descriptors and the user register state) between
    the unwind library and the personality routine and landing pad.  Only



	Jakub